Social/cultural factors, such as copying behavior, may have considerable effects on a female's decision regarding with whom to mate. The strongest evidence for female mate copying comes from work on the guppy, Poecilia reticulata. In addition to providing the first controlled experimental work on mate copying, subsequent work on female mate copying in the guppy has found that young females are more likely to copy the mate choice of old females than vice versa, females will switch their initial preference if they observe another female choose a male which they did not themselves choose, and mate copying can, under some conditions, override genetic predispositions for certain male traits. Despite prior work on mate copying, many of the most fundamental and conceptually intriguing questions on copying and mate choice have yet to be investigated experimentally, in this system, or any other. To date, my work on cultural transmission and mate choice in guppies has focused on the behavior of individual females. Demonstrating the power of cultural transmission via the behavior of individuals is a critical first step, but it is truly just a first step, in understanding the cultural transmission of social behavior. One of the most potent elements in how cultural transmission shapes behavior focuses on how individual decisions ripple through groups and change the distribution of behavioral choices within a group in a single (or a very few) generations. It is this component of cultural transmission in animals that I propose to work on over the next few years. The studies proposed here have implications for developmental and social psychology, as well as evolutionary and behavioral ecology. Although psychologists have studied copying behavior in many contexts, it has been difficult to assess the relative contribution that genetic and social factors (such as copying) may have on the manifestation of a particular behavior. The guppy system allows one to overcome this hurdle as well, and has the added benefit of examining the dynamics of cultural transmission with respect to a behavior - mate choice - that is of significant interest to numerous different fields in psychology. In fact, my initial work on mate copying in guppies has facilitated collaboration with Dr. Michael Cunningham, a social psychologist. Based on the questions developed in the guppy research, we examined human mate copying behavior. We have found some evidence of mate copying in a study using written surveys. Here, I propose to continue my work with Dr. Cunningham, and examine mate copying in an experimental scenario that moves away from a written survey, and provides a more realistic evaluation of human mate copying.